Inner Helmholtz Layer Regulating Additive for Ultrastable Aqueous Zinc Ion Batteries

Zinc-ion batteries (ZIBs) have emerged as a highly promising energy storage technology, offering exceptional energy density, inherent safety, and cost-effectiveness. However, their widespread adoption is hindered by challenges such as dendrite formation and parasitic reactions at the anode/electrolyte interface. In this study, 1-methyl-2-pyridone (MPO) is introduced as an organic additive to the aqueous electrolyte of ZIBs. Benefiting from the narrow molecular orbital band gap, the MPO additive effectively disrupts the hydrogen bonding network among water molecules, optimizes the solvation structure, and modifies the inner Helmholtz layer, thereby enabling a dendrite-free, highly reversible, and long-cycling Zn anode. As a result, Zn∥Zn symmetric cells achieve an exceptional cycle life of over 8000 h at a current density of 1 mA cm –2 with a capacity of 1 mAh cm –2 , while Zn∥Cu cells attain a remarkable Coulombic efficiency of 99.6%. Moreover, a full cell incorporating a V 2 O 5 · x H 2 O cathode delivers a high capacity of 150 mAh g –1 over 2000 cycles at a current density of 2 A g –1 , highlighting the practical potential of this strategy for advanced energy storage systems.